Bogeys using an articulated frame have the advantage of better ground contact for all four wheels of the bogey in particular when passing over distortion of the track: at a transition between a straight and a canted curve; or when passing over track defects.
In the prior art, articulated frames for bogeys comprise two length members and two cross-members, each of the cross-members being secured to one of the length members via a hinge device.
The hinge devices enable each assembled-together length-member and cross-member pair to pivot about the axis defined by the two hinge devices.
FIG. 9 of document U.S. Pat. No. 3,398,700 shows a bogey including an articulated bogey frame comprising a right side beam, a left side beam, a front beam, and a rear beam, the right and left side beams being respectively secured to the front and rear beams, and hinge means disposed respectively between the right and left side beams and the front and rear beams.
Such a prior art bogey frame is shown diagrammatically in accompanying FIG. 1.
The prior art bogey frame is constituted by two hinged-together elements that are generally T-shaped.
The way in which the prior art bogey frame is articulated makes it possible to simplify the so-called "primary" suspension between the axles and the length members.
A major drawback of the prior art articulated bogey is that it does not make it possible to eliminate the primary suspension altogether since each axle is subjected to angular displacement relative to the two length members.
This is because each axle is associated with two half-frames.
The merit of the Applicant lies in proposing a bogey frame made up of two half-frames, in which each of the half-frames is generally L-shaped.
Another drawback of prior art articulated bogey frames is that they are still too bulky.